Assembly of gas expansion elements and method of operating said assembly

ABSTRACT

An assembly of gas expansion elements for a device for converting thermal energy into motor energy in particular for a hot-water motor, wherein the assembly includes two closed pressure containers, both of which are filled with a gas or gas mixture, and both of which have an upper injection opening for hot and cold water. The assembly is provided with a short-circuit pipe between the two pressure containers and the short circuit pipe includes at least one controllable valve for equalizing the closed pressure containers, after the gas or gas mixture has performed its work.

TECHNICAL FIELD

[0001] The invention generally relates to engines and more particularly relates to an arrangement of gas expansion elements for a device for converting thermal energy into motive energy.

BACKGROUND OF THE INVENTION

[0002] During heating and expansion, gases convert a relatively large amount of heat into work, producing in rapid processes, such as the Stirling process, significant losses through dissipation, unfavorable piston control, heat and hunting losses, clearance volume effects, large regenerator resistance, and high speeds.

[0003] From U.S. Pat. No. 4,283,915, an arrangement for converting thermal energy into motive energy is known, which includes an input for hot water and an input for cold water, with a certain temperature difference prevailing between the hot water and the cold water. The hot water and the cold water are led alternately through pipes of a heat exchanger in order to expand and to contract a working fluid. The work cycle is performed above a boiling point of the working fluid. By means of non-return valves, a relatively high pressure for activating the arrangement is guaranteed. Here, the use of the heat exchanger is disadvantageous, because such a heat exchanger has only a greatly limited efficiency for high technical expense and is relatively susceptible to faults depending on the conditions of the media flowing through and around it.

[0004] In addition, DE 197 19 190 C2 discloses an arrangement for converting thermal energy into electrical energy, which consists of a working circuit with a working fluid for driving a fluid flow engine and of a plurality of heat exchangers that carry alternating flows of cold and hot medium. In each of the heat exchangers, there is an expansion element, which expands and contracts as a function of the temperature of the medium. The temperature-dependent expansions and contractions of this expansion element are fed over an intermediate storage device to the working circuit. For storing a force, an intermediate storage device formed as a spring is allocated to each heat exchanger, wherein each spring is connected to the piston of a pressure cylinder, whose working space is connected by means of controllable valves by way of suction and pressure lines to a working oil circuit, which drives a turbine with a generator. This arrangement features a relatively complex setup, particularly due to the intermediate storage devices formed as springs, and includes the previously mentioned disadvantages of a heat exchanger.

[0005] Furthermore, WO 00/53898 discloses a gas expansion element for an arrangement for converting thermal energy into motive energy, particularly for a hot-water motor, consisting of a closed pressure container filled with a gas or gas mixture, which is operatively connected over an displacement piston to the arrangement. The pressure container has an upper inlet opening for hot and cold water and a lower water discharge opening. A hot-water motor includes complementary pairs of pressure containers with associated fluid piston pumps, which act on a working circuit of a water turbine. During a first cycle process, a hot, expanding gas or gas mixture is present in the first pressure container and the second pressure container contains a cold, contracting gas or gas mixture. For a subsequent second cycle process, the gas or gas mixture of the first pressure container is cooled through injection of cold water and the gas or gas mixture of the second pressure container is heated by injecting hot water. The gas volumes change correspondingly. Thus, e.g., the entire gas mixture still containing hot water in the first pressure container is flushed with cold water until the temperature in this pressure container drops to a discharge level. In this way, the thermal energy that is still present is lost.

[0006] The object of the invention is to create an arrangement of gas expansion elements of the initially mentioned type, as well as a method for operating the arrangement, with which a relatively high efficiency can be achieved with low technical expense.

[0007] According to the invention, there is a bypass pipe with at least one controllable valve for pressure equalization between the pressure containers after the performance of the work of the gas or gas mixture.

[0008] At the end of the work phase, there is a pressure difference between the two pressure containers. Due to the pressure difference between the hot gas mixture of one pressure container and the cold gas mixture of the other pressure container, a pressure equalization takes place between the two pressure containers after the opening of the controlled valves. For this equalization, due to the heat flow, the heat energy still present in one pressure container is used for heating the gas mixture of the other pressure container up to an equalization temperature. Simultaneously, the amount of gas in the pressure container with the expanding gas or gas mixture increases, which brings with it an increase in the pressure difference between the two pressure containers, and thus an increase in efficiency. The valve is opened after the performance of the work of the gas mixture through corresponding expansion or contraction and the associated driving of an displacement piston of the hot-water motor, wherein the piston is formed as a fluid piston pump. Because the gas mixture heated in a first cycle process is cooled in a subsequent second cycle process, it is necessary to reduce the temperature of the gas mixture of this vessel below the equalization temperature, wherein the existing residual heat of the gas mixture is used for heating the cooled gas mixture, which is now to be heated. Thus, the residual heat is not lost without being used, which achieves a relatively high efficiency with a relatively low technical expense. The residual heat is also not led into the working circuit of the hot-water motor, from which it would have to be removed again. In addition, in the pressure container to be heated, there is a large amount of gas mixture, which finally performs the work for driving the hot-water motor through its expansion, and simultaneously the amount of the gas mixture to be cooled is smaller in the other pressure container and the reduction of the output pressure relative to a conventional arrangement is larger, which leads to a shift in the corresponding p-V diagram in the desired direction.

[0009] According to an advantageous configuration of the invention, the bypass pipe is arranged in the upper region of the pressure container. In this region of the pressure container, in which a flange or a cover is located, there is neither hot or cold water, therefore the gas mixture can be led undisturbed through the opened valve into the bypass pipe. Furthermore, the gas mixture with the highest temperature is located approximately in this region.

[0010] In order to avoid clearance volumes in the pressure containers, preferably a controllable valve is arranged in the region in the bypass pipe directly adjacent to the associated pressure container.

[0011] The present invention also includes a method for operating an arrangement for which hot and cold water is alternately injected into the pressure container, such that after the transfer of the work of the gas or gas mixture of one of the pressure containers, the gas or gas mixture is led through openings of the controllable valve by way of the bypass pipe into the other pressure container.

[0012] After the gas mixture has brought the displacement piston formed as a fluid piston pump of the hot-water motor into a predetermined position due to its expansion or contraction produced through heat or cold charging, the valve in the bypass pipe is opened for pressure equalization between the two pressure containers. Through the resulting convection of the hot gas mixture, an equalization temperature is set between the two pressure containers. This produces a significant increase in the efficiency of the arrangement operated according to the method according to the invention, because the existing residual pressure and the existing residual heat energy of the gas mixture of one pressure container are used for increasing the pressure and for heating the gas mixture of the other pressure container.

[0013] According to a preferred configuration of the invention, one portion of the gas or gas mixture is led into the other pressure container after the transfer of the usable expansion work of the gas or gas mixture of a pressure container. Because an economically significant work phase of the gas mixture does not correspond to the entire expansion period of the gas mixture, the work phase, thus the usable expansion work of the gas mixture, is completed by the opening of the valve and its residual energy is used for increasing the pressure and for heating the gas mixture of the other pressure container.

[0014] Advantageously, two controllable valves of the bypass pipe are opened and closed approximately simultaneously. Thus, the pressure equalization, which produces a heat flow from one pressure container to the other, is selectively controlled and the clearance volume in the bypass pipe is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1, a schematic representation of an arrangement according to the invention,

[0016]FIG. 2, a diagram for representing a cycle process of the arrangement, and

[0017]FIG. 3, a pressure-time diagram for representing the cycle process of the arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The arrangement includes a storage container 1 for water with a level indicator 2. The container is connected by way of pipes 3 to a cooling device 4 and a heating device 5. From the cooling device 4 and the heating device 5, a corresponding pipe 6 leads to a regulated opening 7, 8 of a pressure container 9, 10. The closed pressure containers 9, 10 are filled with a gas mixture. Between the two pressure containers 9, 10 there is a bypass pipe 11, which has in the region of each pressure container 9, 10 a controllable valve 12, 13. At the lower end of each pressure container 9, 10, there is an outlet opening 14, 15, which is coupled to a working circuit 16, which includes two fluid piston pumps 17, 18 of a hot-water motor and a turbine 19 with a generator. Furthermore, a pump 21 is inserted in the working circuit 16 connected to the storage container 1 by way of a line 20.

[0019] For operating the arrangement, hot water is prepared in the heating device 5, which is led over the first inlet opening 7 into the first pressure container 9. When injecting the hot water into the first pressure container 9, the gas mixture expands and performs work over an displacement piston 22 of the first fluid piston pump 17. This work is supplied by means of the working circuit 16 to the turbine 19 for converting thermal energy. After the pressure increase and the corresponding pressure drop in the first pressure container 9 resulting after the piston displacement of the first fluid piston pump 17, the water is discharged through the associated discharge opening 14. Simultaneously, in the cooling device 4, cold water is prepared, which is led by way of the second inlet opening 8 into the second pressure container 10. While injecting cold water into the second pressure container 10, the gas mixture contracts and likewise performs work over the displacement piston 22 of the second fluid piston pump 18. After the transfer of the usable expansion or contraction work of the gas mixture, the two valves 12, 13 of the bypass pipe 11 are opened and a temperature equalization up to an equalization temperature between the first pressure container 9 and the second pressure container 10 occurs due to the pressure equalization. Then hot water is injected into the second pressure container 10 and cold water is injected into the first pressure container 9. Because the gas mixture of both pressure containers 9, 10 is at the equalization temperature, unnecessary heating or cooling of the corresponding gas mixture is not required, whereby the arrangement has a relatively high efficiency.

[0020] In the p-V diagram according to FIG. 2, the cycle process of a conventional arrangement is compared with an example arrangement according to the invention, wherein the pressure-temperature curves of a conventional arrangement are shown with continuous lines and the curves of the arrangement according to the invention are shown with dashed lines. Accordingly, the work W′ performed by a conventional arrangement is smaller than the work W performed by an arrangement according to the invention.

[0021] The pressure-time (p-t) diagram according to FIG. 3 shows at the beginning a conventional profile of the process, for which the pressure p′_(max) of the first pressure container 8 falls to the pressure p′_(min), wherein at time t_(e) cold water is injected and the gas mixture performs work in the time period Δt_(a). The pressure of the second pressure container 10 increases from the pressure p′_(min) to the pressure p′_(max), wherein at time t_(e) hot water is injected into the second pressure container 10 and the gas mixture likewise performs work in the time period Δt_(a) for driving the fluid piston pump 14. During the time period Δt₁, no work is performed and the residual pressure in the pressure containers 9, 10 is lost for the system. After the coupling of the first pressure container 9 with the second pressure container 10 by means of the bypass pipe 11, at time t_(k) the valves 12, 13 are opened and a pressure equalization occurs between the first pressure container 9 and the second pressure container 10. Thus, with the expanding gas mixture, a relatively large amount of gas mixture is located in the first pressure container 9 and in the second pressure container 10 there is a correspondingly reduced amount of gas mixture. Simultaneously, an approximate equalization temperature is set in the pressure containers 9, 10 due to the heat flow. After the pressure equalization through the bypass of the two pressure containers 9, 10, at time t_(e), hot or cold water is injected, whereby due to the different distribution of gas mixture amounts, the pressure p_(max) or p_(min) is achieved in the corresponding pressure container 9, 10 and thus the pressure difference Δp relative to the conventional profile of the process. 

1-7. (canceled).
 8. Arrangement of gas expansion elements for a device for converting thermal energy into motive energy, comprising: first and second closed pressure containers filled with a gas or gas mixture, wherein said first and second containers are operatively connected to the device and each include a respectively associated upper injection opening for hot and cold water, a bypass pipe connecting said first and second containers with at least one controllable valve disposed in series with said bypass pipe for pressure equalization between the pressure containers after the gas or gas mixture has performed its work.
 9. Arrangement according to claim 8, wherein the bypass pipe is arranged in an upper region of at least one of said first and second containers.
 10. Arrangement according to claim 8, wherein the controllable valve is arranged in series with the bypass pipe in a region in the bypass pipe directly adjacent to at least one of said first and second containers.
 11. Arrangement according to claim 8, wherein the bypass pipe is heat-insulated with the at least one controllable valve.
 12. Method for operating an arrangement of gas expansion elements for which hot and cold fluid is alternately injected into pressure containers, comprising the step of: transferring the fluid to one of the first or second pressure containers, directing the fluid through openings of a controllable valve placed in series with a bypass pipe which communicates between the first and second pressure containers.
 13. Method according to claim 12, wherein after the transfer of usable expansion work of the fluid in one of said first or second pressure containers, a portion of the fluid is led into the other pressure container.
 14. Arrangement according to claim 12, wherein said controllable valve includes first and second controllable valves placed in series with said bypass pipe, wherein said first and second controllable valves are opened and closed approximately simultaneously. 